It is readily appreciated even to the unskilled artisan that a significant contribution to the cost of a retail product packaged in plastic bottles and the like, is the cost of transporting empty bottles to the product filling site. Irrespective of sanitation considerations, especially important when the bottles will be used for food products, movement of large numbers of such containers is labor intensive and energy inefficient. Little choice was given to the product manufacturer, in the past, due to the prohibitive cost of on-site manufacture of the containers. Economics did not justify the purchase and maintenance of molding equipment.
Recently, the advent of and improvements in computer-controlled molding equipment coupled with a significant cost and scale reduction, have rendered installation and maintenance of on-site container manufacturing feasible. These developments have increased the desirability for manufacturers of large quantities of commodity products, such as food, personal hygiene products, fluids for such varied uses including cleaning, auto care, etc., to provide plastic container, on-site manufacturing facilities.
Although solving the transportation cost problem, on-site production of the product containers introduces several areas for concern to the product manufacturer. More particularly, the manufacturer is faced with considerations of, among other things, adequate inventory, storage, sanitation and product damage. The prospect of the container molding equipments breaking down, without sufficient inventory, could lead to unnecessary interruption of the product output from the factory. Accordingly, it is desirable for the manufacturer to maintain an inventory of containers on site which can be employed in the event of such interrupted container production activity.
Another problem faced in on-site storage of containers is aging of the containers. It is obvious that the first-filled containers should be the first manufactured in time (first in - first out). The quality of containers can deteriorate over time. Hence, proper cycling of the container inventory is imperative to avoid accumulation of older containers. Cycling is especially important in certain businesses such as the food industry where it is undesirable to have containers stored for prolonged periods because contaminants, pests and other environmental factors may render the containers unsanitary thereby requiring disposal rather than use.
A further economic consideration is container damage. Where a plastic container remains on the bottom of a pile, not only does it age, but also the combined weight and pressure created by the overlying containers, can damage, distort, and otherwise render the lower containers unmerchantable.
Ever mindful of costs, the manufacturer with on-site container production apparatus must also factor in labor costs associated with production machinery, intra-plant container transport and introduction of the empty containers to the container filling product line. For example, where static bins are used for container storage, substantial labor is necessary to fill, track, cycle, unload and properly effect container transfer to product filling production lines. In proper practice, inventory control requires tracking of containers, especially in the food or pharmaceutical industries. Tracking consumes substantial labor. For example, if once daily, 450 containers having a capacity of one Gaylord (a standard measurement in the industry corresponding to a container measuring approximately 64 cubic feet (4.times.4.times.4)) are properly tracked, two computer entries are made for each move (start and finish) and each entry takes one second, the time dedicated solely to tracking will exceed 10 man hours per month including remedying tracking errors. It is readily appreciated that bulk storage, one input/one output, would amount to considerable labor and cost savings.
Contemplating the foregoing with the advent of on-site container production and the intent of avoiding certain of the aforementioned problems, continuous-feed and cycle storage silos for plastic product containers have come into vogue. Commonly, these bulk storage units feature hard, inflexible walls and are associated with automatic conveying means from the unit to the production line. In practice, the hard-walled units have experienced limited acceptance due to their inflexible adaptability and the considerable manufacturing, construction and labor costs. Essentially, once installed, it is expensive and difficult to modify a hard-walled unit in order to adapt to changing requirements of the manufacturer.
Recognizing the limitations of hard-walled units, certain soft-walled product container storage silos have been introduced to the market. The advantages of such units include reduced installation expenses of up to 40%, and comparable strength, and greater adaptability and flexibility in use. The soft-walled units generally contain a fabric/polymeric liner suspended from a steel frame having an open top and a conveyor means disposed along the bottom to transport empty containers to the production line. Although soft-walled units are usually satisfactory for their intended purpose, several shortcomings in their use are identifiable.
For example, unless the fabric liner is properly mounted to the frame, it can warp and cause significant product stacking leading to damaging weight concentration on bottom-most containers. Furthermore, where a weak fabric liner is employed, concentrated excess loading may cause damage to the liner, itself. It is also known that discharge jamming occurs. Empty plastic containers stored in soft-walled silos can lodge in and block the container conveyor exit or chute whereupon it is necessary for a workman to clear the product chute either by climbing into the storage silo or accessing the exit chute under the silo.
The final problem noted here, is article distribution within the storage silo. Uneven distribution of product containers in the storage silo will result in a failure to utilize the available storage volume. It is readily apparent that empty containers fed into the silo by a conveyor linked to the blow-molding apparatus will form a pile bearing the likeness of a conical pyramid from the point of exit from the conveyor. Pyramiding not only leads to unutilized space in the storage silo, itself, but also, especially in the context of the plastic/fabric wall, can create selected points of excess loading thereby causing damage to the lower-most containers. Moreover, the uneven distribution of containers in the silo near its discharge can induce jamming.